Merge pull request #10156 from wangjohn/grouping_thread_locals

Grouping thread locals in ActiveRecord

7 files changed, 47 insertions, 14 deletions

diff --git a/activerecord/lib/active_record.rb b/activerecord/lib/active_record.rb
index 3bfc6772b2..249eabfd7d 100644
--- a/activerecord/lib/active_record.rb
+++ b/activerecord/lib/active_record.rb
@@ -50,6 +50,7 @@ module ActiveRecord
   autoload :Querying
   autoload :ReadonlyAttributes
   autoload :Reflection
+  autoload :RuntimeRegistry
   autoload :Sanitization
   autoload :Schema
   autoload :SchemaDumper
diff --git a/activerecord/lib/active_record/connection_handling.rb b/activerecord/lib/active_record/connection_handling.rb
index 1e03414c29..3f175988db 100644
--- a/activerecord/lib/active_record/connection_handling.rb
+++ b/activerecord/lib/active_record/connection_handling.rb
@@ -54,11 +54,11 @@ module ActiveRecord
     end
 
     def connection_id
-      Thread.current['ActiveRecord::Base.connection_id']
+      ActiveRecord::RuntimeRegistry.instance.connection_id
     end
 
     def connection_id=(connection_id)
-      Thread.current['ActiveRecord::Base.connection_id'] = connection_id
+      ActiveRecord::RuntimeRegistry.instance.connection_id = connection_id
     end
 
     # Returns the configuration of the associated connection as a hash:
diff --git a/activerecord/lib/active_record/core.rb b/activerecord/lib/active_record/core.rb
index afa1766615..7a8408155a 100644
--- a/activerecord/lib/active_record/core.rb
+++ b/activerecord/lib/active_record/core.rb
@@ -80,11 +80,11 @@ module ActiveRecord
       class_attribute :default_connection_handler, instance_writer: false
 
       def self.connection_handler
-        Thread.current[:active_record_connection_handler] || self.default_connection_handler
+        ActiveRecord::RuntimeRegistry.instance.connection_handler || self.default_connection_handler
       end
 
       def self.connection_handler=(handler)
-        Thread.current[:active_record_connection_handler] = handler
+        ActiveRecord::RuntimeRegistry.instance.connection_handler = handler
       end
 
       self.default_connection_handler = ConnectionAdapters::ConnectionHandler.new
diff --git a/activerecord/lib/active_record/log_subscriber.rb b/activerecord/lib/active_record/log_subscriber.rb
index c1ba524c84..69371a1dab 100644
--- a/activerecord/lib/active_record/log_subscriber.rb
+++ b/activerecord/lib/active_record/log_subscriber.rb
@@ -3,11 +3,11 @@ module ActiveRecord
     IGNORE_PAYLOAD_NAMES = ["SCHEMA", "EXPLAIN"]
 
     def self.runtime=(value)
-      Thread.current[:active_record_sql_runtime] = value
+      ActiveRecord::RuntimeRegistry.instance.sql_runtime = value
     end
 
     def self.runtime
-      Thread.current[:active_record_sql_runtime] ||= 0
+      ActiveRecord::RuntimeRegistry.instance.sql_runtime ||= 0
     end
 
     def self.reset_runtime
diff --git a/activerecord/lib/active_record/runtime_registry.rb b/activerecord/lib/active_record/runtime_registry.rb
new file mode 100644
index 0000000000..3f0ac68143
--- /dev/null
+++ b/activerecord/lib/active_record/runtime_registry.rb
@@ -0,0 +1,32 @@
+require 'active_support/per_thread_registry'
+
+module ActiveRecord
+  # This is a registry class for storing local variables in active record. The
+  # class allows you to access variables that are local to the current thread.
+  # These thread local variables are stored as attributes in the
+  # +RuntimeRegistry+ class.
+  #
+  # You can access the thread local variables by calling a variable's name on
+  # the +RuntimeRegistry+ class. For example, if you wanted to obtain the
+  # connection handler for the current thread, you would invoke:
+  #
+  #   ActiveRecord::RuntimeRegistry.instance.connection_handler
+  #
+  # The +PerThreadRegistry+ module will make a new +RuntimeRegistry+ instance
+  # and store it in +Thread.current+. Whenever you make a call for an attribute
+  # on the +RuntimeRegistry+ class, the call will be sent to the instance that
+  # is stored in +Thread.current+.
+  #
+  # Note that you can also make the following call which would provide an
+  # equivalent result as the previous code:
+  #
+  #   ActiveRecord::RuntimeRegistry.connection_handler
+  #
+  # However, this is less performant because it makes a call to +method_missing+
+  # before it sends the method call to the +instance+.
+  class RuntimeRegistry
+    extend ActiveSupport::PerThreadRegistry
+
+    attr_accessor :connection_handler, :sql_runtime, :connection_id
+  end
+end
diff --git a/activerecord/lib/active_record/scoping.rb b/activerecord/lib/active_record/scoping.rb
index f108ab0fe0..6ab36a23a7 100644
--- a/activerecord/lib/active_record/scoping.rb
+++ b/activerecord/lib/active_record/scoping.rb
@@ -1,3 +1,5 @@
+require 'active_support/per_thread_registry'
+
 module ActiveRecord
   module Scoping
     extend ActiveSupport::Concern
@@ -34,7 +36,7 @@ module ActiveRecord
     # to get the current_scope for the +Board+ model, then you would use the
     # following code:
     #
-    #   registry = ActiveRecord::Scoping::ScopeRegistry.current
+    #   registry = ActiveRecord::Scoping::ScopeRegistry.instance
     #   registry.set_value_for(:current_scope, "Board", some_new_scope)
     #
     # Now when you run:
@@ -48,12 +50,10 @@ module ActiveRecord
     #   ActiveRecord::Scoping::ScopeRegistry.set_value_for(:current_scope,
     #       "Board", some_new_scope)
     class ScopeRegistry # :nodoc:
-      class << self
-        delegate :value_for, :set_value_for, to: :current
+      extend ActiveSupport::PerThreadRegistry
 
-        def current
-          Thread.current["scope_registry"] ||= new
-        end
+      class << self
+        delegate :value_for, :set_value_for, to: :instance
       end
 
       VALID_SCOPE_TYPES = [:current_scope, :ignore_default_scope]
diff --git a/activerecord/test/cases/base_test.rb b/activerecord/test/cases/base_test.rb
index e57dbd5a09..83fc0b48f9 100644
--- a/activerecord/test/cases/base_test.rb
+++ b/activerecord/test/cases/base_test.rb
@@ -1377,9 +1377,9 @@ class BasicsTest < ActiveRecord::TestCase
     UnloadablePost.send(:current_scope=, UnloadablePost.all)
 
     UnloadablePost.unloadable
-    assert_not_nil ActiveRecord::Scoping::ScopeRegistry.current.value_for(:current_scope, "UnloadablePost")
+    assert_not_nil ActiveRecord::Scoping::ScopeRegistry.instance.value_for(:current_scope, "UnloadablePost")
     ActiveSupport::Dependencies.remove_unloadable_constants!
-    assert_nil ActiveRecord::Scoping::ScopeRegistry.current.value_for(:current_scope, "UnloadablePost")
+    assert_nil ActiveRecord::Scoping::ScopeRegistry.instance.value_for(:current_scope, "UnloadablePost")
   ensure
     Object.class_eval{ remove_const :UnloadablePost } if defined?(UnloadablePost)
   end